Arrival of Dave disturbed the Top End (6)
I believe the answer is:
advent
'arrival of' is the definition.
(I've seen this before)
'dave disturbed the top end' is the wordplay.
'disturbed' indicates an anagram (the order of letters is disturbed).
'the top end' becomes 'nt' (I can't explain this - if you can you should give a lot more credence to this answer).
'dave' with letters rearranged gives 'adve'.
'adve'+'nt'='ADVENT'
Can you help me to learn more?
(Other definitions for advent that I've seen before include "Season for a candle?" , "approach" , "Time approaching Christmas" , "Pre-Christmas season for Christians" , "Forty days preceding Christmas" .)